To transport a moving picture film, moving picture cameras have motor and transmission devices, as well as a moving diaphragm device, by means of which the light path is interrupted during the film transport from the lens to the focal plane. These moving devices generate mechanical vibrations which cannot be eliminated in the camera itself. To keep the inherent noise level of such a moving picture camera to a minimum, it is necessary to prevent the transmission of these unavoidable vibrations to the external skin of the film camera.
For soundproofing, damping materials such as rubber and similar materials are used between the moving parts of the moving picture camera and the camera housing, but they have the disadvantage of low mechanical stability, so that a frequent readjustment is necessary, since the camera lens is fastened to the camera housing, while the focal plane of the moving picture film runs in the vicinity of the moving parts of the film camera, so that any displacement between the camera housing and the camera skeleton supporting the moving parts of the moving picture camera causes a loss of sharpness of the image or image shifts. The prior art has proposed various measures to solve this problem.
Federal Republic of Germany Patent Publication DE 30 49 150 C2 discloses a moving picture camera which consists of an inner camera and an external camera housing. The inner camera includes an image aperture, a film transport mechanism, a ground glass disc or screen, a rotating reflecting diaphragm, an apparatus for the transport of the moving picture film from a film feeding spool roll to a film take-up spool, as well as a film magazine and a motor/transmission unit to drive all the moving parts of the camera.
A changeable shooting lens is fastened to the external camera housing by means of a lens mount. The internal camera is supported on the external camera housing by components which make it possible to change the position of the inner camera in relation to the external camera housing when the position of the moving picture camera changes.
To compensate for these allowable changes in position of the internal camera in relation to the external camera housing, there is an apparatus which, when there are such changes in the position of the camera, move the inner camera relative to the external camera housing back into a specified ideal position, in which the required sharpness of the image is guaranteed. This return apparatus consists of a two-armed lever, which is mounted in a fulcrum point in a connector connected to the external camera housing, while the one lever arm is rotatably fastened to the inner camera, and the other lever arm can be activated to change the position of the inner camera.
This device of the prior art naturally reacts to compensate for movements of the moving picture camera, but it cannot prevent short-term shifts of the flange focal distance between the lens plane fastened to the external camera housing and the focal plane fastened to the inner camera or to the camera skeleton. Moreover, the compensation apparatus is relatively complex and expensive, and takes up additional space in the moving picture camera.
U.S. Pat. No. 4,174,157 discloses a moving picture camera which is composed of an inner camera and an external camera housing, whereby the moving parts of the camera are fastened to the inner camera, while the external camera housing has a lens mount. Between the inner camera and the external camera housing, there are soundproof connecting elements, which have an externally threaded rod which can be screwed into the camera housing or into the inner camera. The externally threaded rod is held in an internally threaded sleeve, between which and an externally threaded bearing bush there is a hollow cylindrical elastomer insert.
The externally threaded rod, the internally threaded sleeve, the elastomer insert and the externally threaded bearing bush are oriented coaxially to one another, whereby the externally threaded bearing bush is held by an internally threaded element on the other part of the camera housing or the inner camera. If, after the loosening of the externally threaded rod, the externally threaded bearing bush rotates inside the internally threaded sleeve, it becomes possible to adjust the lateral orientation of the inner camera and the movable camera parts in relation to the camera housing, and thus the lens mount.
On this apparatus of the prior art for soundproofing the inner camera in relation to the external camera housing, a constant readjustment of the soundproofing connecting elements is necessary to guarantee the specified flange focal distance between the lens plane and the focal plane.